In the prior art, there is a known SAW filter which, by taking advantage of surface acoustic waves (SAW) which are transmitted along the surface of a piezoelectric material such as, for example, quartz or the like, eliminates noise by only allowing to pass a frequency signal of a predetermined frequency band.
With this kind of SAW filter, it is possible to obtain a higher attenuation characteristic as compared to quartz by including a piezoelectric material such as, for example, langasite (La3Ga5SiO14) or the like, which has a crystalline structure just like that of quartz.
However, with a SAW filter according to the prior art such as the one described above, it sometimes happens that the attenuation characteristic undesirably deteriorates, according to the structure of the printed substrate upon which it is mounted, and there is a fear that it may no longer be possible to obtain the desired attenuation characteristic.
The present invention is one which has been made in consideration of the above described circumstances, and it takes as its first objective to provide: a printed substrate which is capable of preventing undesirable deterioration of the attenuation characteristic of a filter such as, for example, a SAW filter or the like; to an amplification device, a distribution device, a composition device, a switchover device, a signal reception device, and a signal transmission device in a communication system which comprises said printed substrate; to a mobile station device and a base station device in a mobile communication system which comprises said printed substrate; and to a wireless communication device which comprises said printed substrate.
Furthermore, with an electronic component which comprises a SAW filter of this type, a conductive protective member such as, for example, one in sheet form or the like is carried over a SAW filter which is mounted upon an appropriate electronic circuit substrate such as a printed substrate or the like; and, furthermore, it is arranged to reduce the influence of electromagnetic radiation and noise by covering the surroundings of the SAW filter by a shield case which is made from metal or the like.
However, with an electronic component which comprises a SAW filter according to the prior art such as the one described above, according to the shape and the size of the conductive protective member which is carried upon the SAW filter, it sometimes happens that the attenuation characteristic is undesirably deteriorated, and there is a fear that it may no longer be possible to obtain the desired attenuation characteristic.
The present invention is one which has been made in consideration of the above described circumstances, and it takes as its second objective to provide: an electronic component which comprises a shield structure which is capable of preventing undesirable deterioration of the attenuation characteristic of a filter such as, for example, a SAW filter or the like; to an amplification device, a distribution device, a composition device, a switchover device, a signal reception device, and a signal transmission device in a communication system which comprises said electronic component; to a mobile station device and a base station device in a mobile communication system which comprises said electronic component; and to a wireless communication device which comprises said electronic component.